minfrog error: field cannot override anything but property

buildit.sh

MINFROG=~/dart_bleeding/dart/frog/minfrog
$MINFROG --compile-only --out=Test1.dart.js Test1.dart 
$MINFROG --compile-only --out=Test2.dart.js Test2.dart 

Test1.dart

#import('dart:html');

class A {
  List _l;
}

class B extends A {
  List _l;
}

main() {
  new B();
  print('Hello, Dart!');
}

Test2.dart

#import('dart:html');

class A {
  List _l;
}

class B extends A {
  List _l;
  B() { _l = new List(); }
}

main() {
  new B();
  print('Hello, Dart!');
}

One Test1 compiles without any errors. Test2 fails with the following error message:

Test2.dart:8:3: error: field cannot override anything but property List _l; ^^^^^^^^ Test2.dart:4:3: error: field cannot override anything but property List _l; ^^^^^^^^ /Users/adam/dart_bleeding/dart/client/html/release/htmlimpl.dart:18155:12: warning: type "dom.FileReader" is not assignable to "html.FileReader" return new dom.FileReader(); ^^^^^^^^^^^^^^^^^^^^ compilation failed with 1 errors